1. Field of the Invention
This invention relates to heat-stable oil-in-water emulsions which contain hydrolyzed protein. These emulsions are stabilized by a hydrolyzed glycerol derivative. The invention further relates to dried or non-dried protein hydrolyzate-containing products and foods in which an emulsion of the above-described type is used. One objective in particular is to produce baby food or a food of reduced allergenicity, using the present invention.
2. Description of the Prior Art
Proteins, in particular lactoprotein and soybean protein, are known for their function as stabilizer and/or emulsifier in oil-in-water emulsions. More particularly, lactoproteins impart to milk a stability which remains ensured both during heating, for instance in pasteurization and sterilization steps, and during storage. When proteins are subjected to hydrolysis, this good stability and emulsifying behavior declines rapidly. Thus Kuhler and Stine, in their article in the Journal of Food Science 39 (1974), 379-382, described that a decline in the emulsifying behavior of proteins can be observed at a degree of hydrolysis from 5%. Furthermore, Haque and Kinsella in Milchwissenschaft 42 (1988), 236 described that when hydrolyzed protein is introduced into or present in an already formed stable emulsion, this emulsion destabilizes spontaneously.
Although other stabilizers and emulsifiers than the above-mentioned proteins are known, only a few of them are allowed in human foods. In this context reference is made to EEC directire 89/107 and the new version thereof which has been presented for approval to the European Parliament under no. C207-37 (1992). This directire regulates the use of additives in foods. In particular, it provides that in baby food only the emulsifiers lecithin (E322) and/or the partial fatty-acid ester glycerol monostearate (E471) may be used.
Lecithin is a phospholipid, more particularly a diglyceride of saturated and unsaturated fatty acids, for instance stearin, palmitin, linoleic acid and/or oleic acid, coupled to the choline ester of phosphoric acid, or a mixture of such diglycerides. Lecithin is capable of forming an eminently stable oil-in-water emulsion, in which, as a nitrogen source, principally virtually intact proteins are present. Such an emulsion also remains stable after a heating step. However, when contemplating the preparation of a food of reduced allergenicity or a different food in which protein is present for an appreciable part in hydrolyzed condition, lecithin is not satisfactory as an emulsifier/stabilizer.
The same problem arises when using the above-mentioned glycerol monostearate.